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Catalase

Catalase
Identifiers
Symbol cat
Pfam PF00199
InterPro IPR011614
PROSITE PDOC00395
SCOP 7cat
edit
Catalase
PDB rendering based on 1dgb.
Available structures: 1dgb, 1dgf, 1dgg, 1dgh, 1f4j, 1qqw, 1tgu, 1th2, 1th3, 1th4, 4blc, 7cat, 8cat
Identifiers
Symbol(s) CAT; MGC138422; MGC138424
External IDs OMIM: 115500 MGI88271 HomoloGene55514
EC number 1.11.1.6
RNA expression pattern

More reference expression data

Orthologs
Human Mouse
Entrez 847 12359
Ensembl ENSG00000121691 ENSMUSG00000027187
Uniprot P04040 Q3TVZ1
Refseq NM_001752 (mRNA)
NP_001743 (protein)
NM_009804 (mRNA)
NP_033934 (protein)
Location Chr 11: 34.42 - 34.45 Mb Chr 2: 103.25 - 103.29 Mb
Pubmed search [1] [2]


Catalase is a common enzyme found in nearly all living organisms. Its functions include catalyzing the decomposition of hydrogen peroxide to water and oxygen.[1] Catalase has one of the highest turnover rates of all enzymes; one molecule of catalase can convert millions of molecules of hydrogen peroxide to water and oxygen per second.[2]

Catalase is a tetramer of four polypeptide chains, each over 500 amino acids long.[3] It contains four porphyrin heme (iron) groups that allow the enzyme to react with the hydrogen peroxide. The optimum pH for catalase is approximately 7,[4] while the optimum temperature varies by species.[5]

History

Catalase was first noticed as a substance in 1811 when Louis Jacques Thénard, who discovered H2O2 (hydrogen peroxide), suggested that its breakdown is caused by a substance.

In 1900 Oscar Loew was the first to give it the name catalase, and found its presence in many plants and animals[6]. In 1937 catalase from beef liver was crystallised by James B. Sumner [7] and the molecular weight worked out in 1938[8]. In 1969 the amino acid sequence of bovine catalase was worked out[9]. Then in 1981, the 3D structure of the protein was revealed[10].

Action of catalase

The reaction of catalase in the decomposition of hydrogen peroxide is:

2 H2O2 ����� 2 H2O + O2[11]

In microbiology, the catalase test is used to differentiate between bacterial species in the lab.[3] The test is done by placing a drop of hydrogen peroxide on a microscope slide. Using an applicator stick, a scientist touches the colony and then smears a sample into the hydrogen peroxide drop. If bubbles or froth forms, the organism is said to be catalase-positive; if not, the organism is catalase-negative.[4] This test is particularly useful in distinguishing staphylococci and micrococci, which are catalase-positive, from streptococci and enterococci, which are catalase-negative.[5] While the catalase test alone cannot identify a particular organism, combined with other tests, it can aid diagnosis. The presence of catalase in bacterial cells depends on both the growth condition and the medium used to grow the cells.

Molecular mechanism

While the complete mechanism of catalase is not currently known, the reaction is believed to occur in two stages:

H2O2 + Fe(III)-E → H2O + O=Fe(IV)-E(.+)
H2O2 + O=Fe(IV)-E(.+) → H2O + Fe(III)-E + O2[12]
Here Fe()-E represents the iron centre of the heme group attached to the enzyme. Fe(IV)-E(.+) ís a mesomeric form of Fe(V)-E, meaning that iron is not completely oxidized to +V but receives some "supporting electron" from the heme ligand. This heme has to be drawn then als radical cation (.+).

As hydrogen peroxide enters the active site, it interacts with the amino acids Asn147 (asparagine at position 147) and His74, causing a proton (hydrogen ion) to transfer between the oxygen atoms. The free oxygen atom coordinates, freeing the newly-formed water molecule and Fe(IV)=O. Fe(IV)=O reacts with a second hydrogen peroxide molecule to reform Fe(III)-E and produce water and oxygen.[12] The reactivity of the iron center may be improved by the presence of the phenolate ligand of Tyr357 in the fifth iron ligand, which can assist in the oxidation of the Fe(III) to Fe(IV). The efficiency of the reaction may also be improved by the interactions of His74 and Asn147 with reaction intermediates.[12] In general, the rate of the reaction can be determined by the Michaelis-Menten equation.[6]

Catalase can also oxidize different toxins, such as formaldehyde, formic acid, and alcohols. In doing so, it uses hydrogen peroxide according to the following reaction:

H2O2 + H2R → 2H2O + R

Again, the exact mechanism of this reaction is not known.

Any heavy metal ion (such as copper cations in copper(II) sulfate) will act as a noncompetitive inhibitor on catalase. Also, the poison cyanide is a competitive inhibitor of catalase, strongly binding to the heme of catalase and stopping the enzyme's action.

Three-dimensional protein structures of the peroxidated catalase intermediates are available at the Protein Data Bank. This enzyme is commonly used in laboratories as a tool for learning the effect of enzymes upon reaction rates.

Cellular role

Hydrogen peroxide is a harmful by-product of many normal metabolic processes: To prevent damage, it must be quickly converted into other, less dangerous substances. To this end, catalase is frequently used by cells to rapidly catalyze the decomposition of hydrogen peroxide into less reactive gaseous oxygen and water molecules.[13]

The true biological significance of catalase is not always straightforward to assess: Mice genetically engineered to lack catalase are phenotypically normal, indicating that this enzyme is dispensable in animals under some conditions.[14]

Some human beings have very low levels of catalase (acatalesimia), yet show few ill effects. It is likely that the predominant scavengers of H2O2 in normal mammalian cells are peroxiredoxins rather than catalase.

Catalase works at an optimum temperature of 37 °C, which is approximately the temperature of the human body.

Catalase is usually located in a cellular organelle called the peroxisome.[15] Peroxisomes in plant cells are involved in photorespiration (the use of oxygen and production of carbon dioxide) and symbiotic nitrogen fixation (the breaking apart of diatomic nitrogen (N2) to reactive nitrogen atoms).

Hydrogen peroxide is used as a potent antimicrobial agent when cells are infected with a pathogen. Pathogens that are catalase-positive, such as Mycobacterium tuberculosis, Legionella pneumophila, and Campylobacter jejuni, make catalase in order to deactivate the peroxide radicals, thus allowing them to survive unharmed within the host .[7]

Distribution among organisms

All known animals use catalase in every organ, with particularly high concentrations occurring in the liver. One unique use of catalase occurs in bombardier beetle. The beetle has two sets of chemicals ordinarily stored separately in its paired glands. The larger of the pair, the storage chamber or reservoir, contains hydroquinones and hydrogen peroxide, whereas the smaller of the pair, the reaction chamber, contains catalases and peroxidases. To activate the spray, the beetle mixes the contents of the two compartments, causing oxygen to be liberated from hydrogen peroxide. The oxygen oxidizes the hydroquinones and also acts as the propellant. [16]

Catalase is also universal among plants, but not among fungi, although some species have been found to produce the enzyme when growing in an environment with a low pH and warm temperatures.[17]

Very few aerobic microorganisms are known that do not use catalase. [8]. Streptococcus species are an example of aerobic bacteria that do not possess catalase. Catalase has also been observed in some anaerobic microorganisms, such as Methanosarcina barkeri.[18]

Human applications

Hydrogen peroxide
Hydrogen peroxide

Catalase is used in the food industry for removing hydrogen peroxide from milk prior to cheese production.[9] Another use is in food wrappers, where it prevents food from oxidizing.[10] Catalase is also used in the textile industry, removing hydrogen peroxide from fabrics to make sure the material is peroxide-free.[11] A minor use is in contact lens hygiene - a few lens-cleaning products disinfect the lens using a hydrogen peroxide solution; a solution containing catalase is then used to decompose the hydrogen peroxide before the lens is used again.[19] Recently, catalase has also begun to be used in the aesthetics industry. Several mask treatments combine the enzyme with hydrogen peroxide on the face with the intent of increasing cellular oxygenation in the upper layers of the epidermis.

The catalase test is also one of the main three tests used by microbiologists to identify species of bacteria. The presence of catalase enzyme in the test isolate is detected using hydrogen peroxide. This when exposed to a small amount of a bacterial isolate will bubble if the bacteria possess this enzyme.

Pathology

The peroxisomal disorder acatalasia is due to a deficiency in the function of catalase.

See also

References

  1. ^ "Catalase: An Enzyme at Work". Science Education Outreach. Retrieved on 2007-02-11.
  2. ^ "Catalase". Molecule of the Month. RCSB Protein Data Bank (2004-09-01). Retrieved on 2007-02-11.
  3. ^ Boon EM, Downs A, Marcey D. "Catalase: H2O2: H2O2 Oxidoreductase". Catalase Structural Tutorial Text. Retrieved on 2007-02-11.
  4. ^ (1954) The Assay of Catalases and Peroxidases in Methods of Biochemical Analysis, 357. ISBN. 
  5. ^ "A Quantitative Enzyme Study; CATALASE". Retrieved on 2007-02-11.
  6. ^ Loew, Oscar (May 1900). "A New Enzyme of General Occurrence in Organisms". Science 11 (279): 701–2. doi:10.1126/science.11.279.701. 
  7. ^ Sumner, J.B.; Dounce, A. L. (1938). "Cystalline Catalase". Science 87 (18): 284. doi:10.1126/science.87.2256.284. 
  8. ^ Sumner, James B.; Gralen, Nils (Mar 1938). "The Molecular Weight of Crystalline Catalase". Science 87 (2256): 284. doi:10.1126/science.87.2256.284. 
  9. ^ Schroeder WA; Shelton JR; Shelton JB; Robberson B; Apell G. (May 1969). "The amino acid sequence of bovine liver catalase: a preliminary report.". Arch Biochem Biophys 131 (2): 653–5. doi:10.1016/0003-9861(69)90441-X. PMID 4892021. 
  10. ^ Murthy MR; Reid TJ 3rd; Sicignano A; Tanaka N; Rossmann MG. (Oct 1981). "Structure of beef liver catalase.". J Mol Biol 152 (2): 465–99. doi:10.1016/0022-2836(81)90254-0. PMID 7328661. 
  11. ^ "Catalase: A Closer Look". Science Education Outreach. Retrieved on 2007-02-11.
  12. ^ a b c Boon EM, Downs A, Marcey D. "Proposed Mechanism of Catalase in Catalase: H2O2: H2O2 Oxidoreductase". Catalase Structural Tutorial Text. Retrieved on 2007-02-11.
  13. ^ Gaetani G, Ferraris A, Rolfo M, Mangerini R, Arena S, Kirkman H (1996). "Predominant role of catalase in the disposal of hydrogen peroxide within human erythrocytes.". Blood 87 (4): 1595–9. PMID 8608252. 
  14. ^ Ho YS, Xiong Y, Ma W, Spector A, Ho D (2004). "Mice Lacking Catalase Develop Normally but Show Differential Sensitivity to Oxidant Tissue Injury.". J Biol Chem 279 (31): 32804–812. doi:10.1074/jbc.M404800200. PMID 15178682. 
  15. ^ Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002). Peroxisomes, in Molecular Biology of the Cell, 4th ed., Garland. (via NCBI Bookshelf) ISBN 0815332181. 
  16. ^ T Eisner and DJ Aneshansley (1999 Aug). "Spray aiming in the bombardier beetle: photographic evidence.". Proc Natl Acad Sci U S A 96 (17): 9705–9. doi:10.1073/pnas.96.17.9705. PMID 10449758. 
  17. ^ K. Isobe, et al. (2006 Jan). "Production of catalase by fungi growing at low pH and high temperature.". J Biosci Bioeng 101 (1): 73–6. doi:10.1263/jbb.101.73. PMID 16503295. 
  18. ^ Andrei Brioukhanov, Alexander Netrusov, and Rik Eggen. (2006). "The catalase and superoxide dismutase genes are transcriptionally up-regulated upon oxidative stress in the strictly anaerobic archaeon Methanosarcina barkeri.". Microbiology 152: 1671–1677. doi:10.1099/mic.0.28542-0. PMID 16735730. 
  19. ^ U.S. Patent 5,521,091 

External links

for systematic sequence analysis of catalases AND peroxidases see http://peroxibase.isb-sib.ch/


 

The content of this section is licensed under the GNU Free Documentation License (local copy). It uses material from the Wikipedia article "Catalase" modified June 23, 2008 with previous authors listed in its history.